mysqlnd_ms_query_is_select
(PECL mysqlnd_ms >= 1.0.0)
mysqlnd_ms_query_is_select — Find whether to send the query to the master, the slave or the last used MySQL server
Description
$query
) : intFinds whether to send the query to the master, the slave or the last used MySQL server.
The plugins built-in read/write split mechanism will be used to analyze the query string to make a recommendation where to send the query. The built-in read/write split mechanism is very basic and simple. The plugin will recommend sending all queries to the MySQL replication master server but those which begin with SELECT, or begin with a SQL hint which enforces sending the query to a slave server. Due to the basic but fast algorithm the plugin may propose to run some read-only statements such as SHOW TABLES on the replication master.
Return Values
A return value of MYSQLND_MS_QUERY_USE_MASTER
indicates that the query should be send to the MySQL replication
master server. The function returns a value of
MYSQLND_MS_QUERY_USE_SLAVE if the query can be run
on a slave because it is considered read-only. A value of
MYSQLND_MS_QUERY_USE_LAST_USED is returned to recommend
running the query on the last used server. This can either be a MySQL
replication master server or a MySQL replication slave server.
If read write splitting has been disabled by setting
mysqlnd_ms.disable_rw_split, the function will
always return MYSQLND_MS_QUERY_USE_MASTER or
MYSQLND_MS_QUERY_USE_LAST_USED.
Examples
Example #1 mysqlnd_ms_query_is_select() example
<?php
function is_select($query)
{
switch (mysqlnd_ms_query_is_select($query))
{
case MYSQLND_MS_QUERY_USE_MASTER:
printf("'%s' should be run on the master.\n", $query);
break;
case MYSQLND_MS_QUERY_USE_SLAVE:
printf("'%s' should be run on a slave.\n", $query);
break;
case MYSQLND_MS_QUERY_USE_LAST_USED:
printf("'%s' should be run on the server that has run the previous query\n", $query);
break;
default:
printf("No suggestion where to run the '%s', fallback to master recommended\n", $query);
break;
}
}
is_select("INSERT INTO test(id) VALUES (1)");
is_select("SELECT 1 FROM DUAL");
is_select("/*" . MYSQLND_MS_LAST_USED_SWITCH . "*/SELECT 2 FROM DUAL");
?>
The above example will output:
INSERT INTO test(id) VALUES (1) should be run on the master. SELECT 1 FROM DUAL should be run on a slave. /*ms=last_used*/SELECT 2 FROM DUAL should be run on the server that has run the previous query
English translation
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Document created the 30/01/2003, last modified the 26/10/2018
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References
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